Polyester vs. Bare Metal

Can polyester primer be used directly on bare metal? Most tech sheets say yes. I think they are wrong.

  • Yes, polyester might have some ability to adhere to metal, but it's always a gamble. Sometimes it sticks great! Sometimes it doesn't, and it's prepped exactly the same. Yes this applies to all polyester primers, including the Clausen products. 
  • I'm not a chemist, so I can't tell you the technical reasons why. But, I do know what the reality is, and have seen it work, and not work. Products have specific purposes; polyester is meant to build and fill, epoxy is meant to adhere and seal. Each product on their own...fantastic. The two products combined....ehhh, so so, for both the sticking and the filling parts. It turns into a general purpose product, and general purpose products are mediocre at best. 
  • What to do? Spray a light coat of epoxy primer (not self etch) on any bare metal. Let it dry for about a day. Scuff it lightly. Spray your polyester primer. **The epoxy must be dry!! The polyester will delaminate and crack if the epoxy isn't dry enough. So do it right. 
And save yourself and your checkbook a massive headache, and never use any polyester as a sealer on bare metal. That's what epoxy is for if you want to go that route.